Flawed model puts aquifer at risk

The first step in protecting the state's environment is getting the science right. Yet Florida uses a flawed model for assessing how groundwater pumping affects the surrounding landscape. It's irresponsible, and state water managers need to correct it.

Tampa Bay Times staff writer Craig Pittman reported Monday that state water officials base all their permitting decisions on computer models that rely on a false assumption. The models assume the underground area known as the aquifer flows at a steady rate through layers of sand and gravel. In reality, the land beneath is composed of karst, a more porous limestone that is full of holes, both big and small. The difference means that water can travel at a much faster rate than the computer models imply, according to current and former state water officials. The net effect is that pollution can be carried much more quickly into the drinking water supply, and state officials have an inaccurate picture of what pumping may do to regions across the state.

An experiment by a team of scientists in 2010 illustrates the depth of the problem. The team dropped fluorescent dye into wells and sinkholes at Silver Springs. Under the state's model, the dye would move toward the springs in cycles ranging from two to 100 years. But the dye dropped by the team rocketed through the aquifer, crossing half the 100-year distance in only six months. The models are so off-base, said David Still, the former director of the Suwannee River Water Management District, that "they shouldn't be used to make decisions."

Yet the regional water management districts rely on the models in deciding how much pumping to allow and assessing the impact on nearby springs, lakes and wetlands. The state also uses the models as part of its effort to track nitrate pollution that comes from septic tanks and upland runoff. Officials say they can "tweak" the models to take into account any obvious signs of environmental degradation. But that is no substitute for a model that accurately measures the flow rates in Florida's distinct water basins.

The water districts should work with Florida's Department of Environmental Protection to update the Florida models. The process may involve some time and expense, and any final model may be imperfect to some degree given the nature of measuring hollow areas in the ground. But these models must be more precise to provide better protection of both the aquifer and surface water.